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NOT APPLICABLE
NOT APPLICABLE
The present invention relates generally to the field of cabinets for outdoor use for enclosing electronic equipment. More specifically, the invention relates to a passive cooling apparatus for a cabinet that shields the cabinet from solar radiation and extracts heat generated by internal electronic equipment by convection.
Outdoor cabinets are often used to house communications equipment such as racks of cards holding electronic or optical components. Such cabinets are provided at outdoor locations where there is no suitable existing building to hold the equipment and protect it from adverse environmental conditions and where the size of the equipment may be too small to justify a dedicated building. Examples of such cabinets include roadside cabinets for housing electronics for controlling traffic signals or cabinets for telecommunications equipment such as digital loop carrier cards and cellular radio base stations.
Considerations in the design of such cabinets include: thermal management, level of environmental protection, corrosion resistance, strength-to-cost ratio, public safety, aesthetic considerations, vulnerability to vandalism, ease of installation, ease of access to equipment, and level of electromagnetic shielding. There are two main aspects with respect to thermal management: equipment inside the cabinet generates heat which may need to be extracted, and the cabinet may be subject to external sources of heat such as solar radiation.
To avoid deterioration from contaminants and corrosives in the ambient air, cabinets are often designed to prevent ambient air from passing over electronic equipment. Typically, electronic equipment is sealed within the cabinet and fans or a heat exchanger may be used to provide cooling where required. In some cases, the cabinet may be air-conditioned.
Several techniques for the cooling of outdoor electronic equipment cabinets are known. For example, it is known from U.S. Pat. No. 6,088,225 to Parry, et al. and U.S. Pat. No. 3,900,700 to Gaudet to provide a double skin or shield for the sides of an enclosure, which assists in cooling the equipment by the xe2x80x9cchimneyxe2x80x9d effect. A chimney effect is produced in the cavity between the skins. An inlet at the bottom of the cavity allows air in, to flow up the cavity, and out of an outlet at the top of the cavity. Heat from the internal skin is thus extracted from the cabinet by convection and thus the equipment inside the cabinet can be kept cool. Furthermore, heat from solar radiation on the external skin can also be extracted and prevented from reaching the equipment inside.
One disadvantage of these known techniques is that the passive cooling element is incorporated within the structure of the cabinet itself. Hence, positioning of the cabinet may be constrained if full advantage of the passive cooling element is to be achieved. Furthermore, being incorporated within the structure of these known cabinets, the passive cooling elements cannot be readily applied to cabinets having different structures. Furthermore, since the passive cooling element is incorporated within the structure of the cabinet itself, it is expensive to retrofit existing cabinets.
A need therefore exists for an apparatus that will allow for the effective and flexible application of passive cooling techniques to outdoor cabinets of varying structure. Consequently, it is an object of the present invention to obviate or mitigate at least some of the above-mentioned disadvantages.
In accordance with an aspect of the present invention, there is provided a cooling apparatus for attaching to a cabinet housing electronics for protecting electronics from external elements. The cooling apparatus comprises an exterior surface for exposing to the external elements and a coupling for attaching the exterior surface to the cabinet. When the cooling apparatus is attached to a surface of the cabinet, the exterior surface is maintained in a spaced-apart relationship from the cabinet forming an enclosed channel having a pair of openings, one of the openings being located above the other.
It is an advantage of the present invention that this heat removal can be achieved passively without the need for a fan blowing external air across the surface of an air-to-air heat exchanger. The apparatus of the invention uses a heat exchanger surface but rather than utilizing a fan for cooling, it employs natural convection airflow generated by a chimney effect. This chimney effect is achieved by allowing air to enter the bottom and exit from the top of a vertical duct, which is formed by the attachment of a vertical channel to an outer vertical surface of the outdoor cabinet. While this vertical channel provides the advantage of creating additional heat transfer surfaces, its primary purpose is to facilitate the chimney effect in order to enhance the natural convection airflow.